they would disperse the sulfur dioxide,
they had planned to float a balloon over
N orfoIk, at an altitude of a kilometre, and
send a hundred and fifty litres of water
into the air through a hose. After the date
and time of the test was announced, in
the middle of September, more than fifty
organizations signed a petition objecting
to the experiment, in part because they
fear that even to consider engineering the
climate would provide politicians with an
excuse for avoiding tough decisions on
reducing greenhouse-gas emissions. Op-
ponents of the water test pointed out the
many uncertainties in the research
(which is precisely why the team wanted
to do the experiment). The British gov-
ernment decided to put it off for at least
six months.
'When people say we shouldn't even
explore this issue, it scares me," Hunt
said. He pointed out that carbon emis-
sions are heavy, and finding a place to
deposit them will not be easy. "Roughly
speaking, the C02 we generate weighs
three or four times as much as the fuel
it comes from." That means that a
short round-trip journey-say, eight
hundred miles-by car, using two
tanks of gas, produces three hundred
kilograms of C02. "This is ten heavy
suitcases from one short trip," Hunt
said. "And you have to store it where it
,
can t evaporate.
"So I have three questions, Where
are you going to put it? Who are you
going to ask to dispose of this for you?
And how much are you reasonably
willing to pay them to do it?" he con-
tinued. "There is nobody on this planet
who can answer any of those questions.
There is no established place or tech-
nique, and nobody has any idea what it
would cost. And we need the answers
"
now.
Hunt stood up, walked slowly to the
window, and gazed at the manicured
Trinity College green. "I know this is all
unpleasant," he said. "Nobody wants it,
but nobody wants to put high doses of
poisonous chemicals into their body, ei-
ther. That is what chemotherapy is,
though, and for people suffering from
cancer those poisons are often their only
hope. Every day, tens of thousands of
people take them willingly-because
they are very sick or dying. This is how
I prefer to look at the possibility of en-
gineering the climate. I t isn't a cure for
anything. But it could very well turn out
to be the least bad option we are going
h "
to ave.
T he notion of modifYing the weather
dates back at least to the eighteen-
thirties, when the American meteorol-
ogist James Pollard Espy became
known as the Storm King, for his (pre-
scient but widely ridiculed) proposals to
stimulate rain by selectively burning
forests. More recently, the U.S. gov-
ernment project Stormfury attempted
for decades to lessen the force ofhurri-
canes by seeding them with silver io-
dide. And in 2008 Chinese soldiers
fired more than a thousand rockets
filled with chemicals at clouds over
Beijing to prevent them from raining
on the Olympics. The relationship be-
tween carbon emissions and the earth's
temperature has been clear for more
than a century: in 1908, the Swedish
scientist Svante Arrhenius suggested
that burning fossil fuels might help
prevent the coming ice age. In 1965,
President Lyndon Johnson received a
report from his Science Advisory Com-
mittee, titled "Restoring the Qyality of
Our Environment," that noted for the
first time the potential need to balance
increased greenhouse-gas emissions by
"raising the albedo, or the reflectivity,
of the earth." The report suggested that
such a change could be achieved by
spreading small reflective particles over
large parts of the ocean.
While such tactics could clearly fail,
perhaps the greater concern is what
might happen if they succeeded in ways
nobody had envisioned. Injecting sulfur
dioxide, or particles that perform a sim-
ilar function, would rapidly lower the
temperature of the earth, at relatively lit-
tle expense-most estimates put the cost
at less than ten billion dollars a year. But
it would do nothing to halt ocean
acidification, which threatens to destroy
coral reefs and wipe out an enormous
number of aquatic species. The risks of
reducing the amount of sunlight that
reaches the atmosphere on that scale
would be as obvious-and immediate-
as the benefits. If such a program were
suddenly to fall apart, the earth would be
subjected to extremely rapid warming,
with nothing to stop it. And while such
an effort would cool the globe, it might
do so in ways that disrupt the behavior of
the Asian and African monsoons, which
provide the water that billions of people
need to drink and to grow their food.
"Geoengineering" actually refers to
two distinct ideas about how to cool the
planet. The first, solar-radiation man-
agement, focusses on reducing the im-
pact of the sun. Whether by seeding
clouds, spreading giant mirrors in the
desert, or injecting sulfates into the
stratosphere, most such plans seek to
replicate the effects of eruptions like Mt.
Pinatubo's. The other approach is less
risky, and involves removing carbon di-
rectly from the atmosphere and bury-
ing it in vast ocean storage beds or
deep inside the earth. But without a
significant technological advance such
projects will be expensive and may take
many years to have any significant effect.
There are dozens of versions of each
scheme, and they range from plausible
to absurd. There have been proposals to
send mirrors, sunshades, and parasols
into space. Recently, the scientific en-
trepreneur Nathan Myhrvold, whose
company Intellectual Ventures has in-
vested in several geoengineering ideas,
said that we could cool the earth by stir-
ring the seas. He has proposed deploy-
ing a million plastic tubes, each about a
hundred metres long, to roil the water,
which would help it trap more C02.
"The ocean is this giant heat sink," he
told me. "But it is very cold. The bottom
is nearly freezing. If you just stirred the
ocean more, you could absorb the excess
C02 and keep the planet cold." (This is
not as crazy as it sounds. In the center of
the ocean, wind-driven currents bring
fresh water to the surface, so stirring the
ocean could transform it into a well-or-
ganized storage depot. The new water
would absorb more carbon while the old
water carried the carbon it has already
captured into the deep.)
The Harvard physicist Russell Seitz
wants to create what amounts to a giant
oceanic bubble bath: bubbles trap air,
which brightens them enough to reflect
THE NEW YORKER, MAY 14, 2012 99